Field
This disclosure relates to electrochemical devices that convert chemical energy to electrochemical current, and more specifically, to an electrochemical device that may be employed under extreme conditions.
Description of the Related Art
Increasing worldwide energy demands as well as depletion of more easily accessible oilfield reservoirs have pushed exploration to more harsh or extreme environments, such as deep water, as well as geothermal energy drilling. These harsh environments generally involve high pressure and/or high temperature conditions. High pressure and/or high temperature conditions often impose more stringent demands for devices powering downhole equipment. Lithium type batteries have been a power source widely used in oilfield downhole exploration. Many electrical tools in the downhole environment are powered by batteries, and specifically Lithium Thyonil Chloride (LTC) batteries. These batteries are very efficient but can be dangerous to operate and transport. Moreover, depleted battery disposal may be a very demanding process involving strict regulations and procedures.
Downhole batteries and electrical power systems have to withstand extreme temperatures in the downhole environment. Lithium batteries, however, may not be available at high temperatures given the low melting temperature of lithium; such physical properties tend to limit the operational temperature of these types of batteries to less than 200° C. Exceeding these limits with a lithium based battery may result in battery malfunction, performance degradation, and potential battery explosion.
In order to design a battery to withstand high temperatures and high pressures using typical battery technology, several engineering compromises may be used. During the battery discharge, especially at high temperature, gas is created inside the battery. Empty space in the battery housing should be designed for the gas expansion. This empty space reduces the battery useful active volume, while still increasing overall battery size for a desired voltage output. Because of this potential gas creation, battery handling can be dangerous, often involving strict procedures. Additionally, a battery housing is designed so that the battery is not subjected to the well pressure and fluids. Exposure to such high pressures and downhole fluids would typically cause the battery to rupture and/or explode. LTC batteries are sometimes limited to 200° C. because of the lithium/manganese alloy melting point. Thus, there is a need for a battery and battery powered downhole tools that can withstand high downhole pressures and temperatures, and yet do not involve special care for transportation and disposal.